1. Field of the Invention
The present invention pertains to a method and device for controlling and eliminating the deposition and build up of paraffin, salts and other scale sediments on the inside of downhole oil string lines and surface or subsurface oil flow transmission lines used for the transportation of crude oil. More particularly the invention relates to the utilization of a novel coupling device having a liner or a section of the conduit composed of a non magnetic and substantially non electrically conductive material surrounded by at least one magnet held in place by a restraining device and surrounded by a magnetic shield.
The oil tools of the invention may be employed in oil flow transmission lines or incorporated as a coupling in downhole oil strings. The utilization of the combination of a magnet and non magnetic and substantially non electrically conducted conduit disposed between sections of downhole oil string and oil flow transmission lines prevents paraffin and shale materials from depositing on the inside of the downhole oil string and surface flow lines without requiring expensive chemicals or extensive down time normally involved in the clogging or oil transmission lines. Paraffin clogging is particularly a problem in paraffin producing oil territories which is believed to result from a combination of magnetic and electrostatic forces resulting from friction in the flowing of oil in the oil conduit that contributes to the collecting of paraffin, salt and scale deposits on the inside of oil transmission lines.
2. Description of the Prior Art
Paraffin and paraffin clogging from deposits in crude oil has long been recognized as a problem in both pumping crude oil from the ground through the downhole oil string and in the transmission of crude oil through oil pipelines. A variety of mechanical, chemical, electrical heating and magnetic systems have been proposed in the prior art for removing paraffin or reducing the affinity of paraffin to deposit or combine with salt, shale, and result in paraffin clogging of crude oil conduits which as known by those skilled in the oil industry results in significant down time and problems in removing the plugging or clogging of downhole oil strings and above ground flow lines.
The prior art chemical systems for removing paraffin plugging of crude oil transmission lines are costly not only in terms of the amount of chemicals required to treat downhole oil strings and flow lines but also in terms of time in interruption of pumping and problems in the subsequent removal or the chemical solvents and the potential environmental impact of such chemicals. Typical chemical treatments for each oil well range from $150.00 to $600.00 per month per well and irrespective of the foregoing problems have been the procedures currently employed in the field due to cost effectiveness considerations.
As a result an effective mechanical system for removing or preventing paraffin clogging has been sought not only because of environmental considerations but also in view of cost effectiveness in terms of efficiency and the number of mechanical units that are required to maintain a given length of pipe. Unfortunately many of the prior art mechanical systems have not been effective in removing or preventing paraffin clogging or have required an unpractical number of units be placed in the oil transmission line for example every five to seventy five feet which make such systems unfeasible in view of cost and the number of units required and in view of space limitations in downhole oil strings which generally have outside diameters of 3 to 4 inches (7.6 to 10.2 cm) and may be as long as 25,000 feet. Other prior art electromechanical systems which involve heating are expensive to operate and maintain which has resulted in the predominant use of chemicals and hot oils and solvents.
Typically some of the prior art declogging systems employ hot oil, hot water or chemical solvents that are pumped through or back down the downhole oil string to force paraffin clogs back through the downhole oil string casing or through above ground flow lines to remove clogs and accumulations of paraffin, salt and paraffin scale deposits on the inside of the crude oil line from which the crude oil flows. These prior art systems result in substantial down time and costs in terms of heating a sufficient amount of water or oil necessary to melt and dissolve paraffin clogged lines as a result of their length and surrounding environmental conditions of the downhole oil line or the surface or buried oil flow transmission lines. Representative of prior art providing for a paraffin controlled coupling with the introduction of hot oil or other solvent for the removal of paraffin from clogged lines is U.S. Pat. No. 3,085,629. Consequently in recent years chemicals have been preferred in view of their effectiveness and cost ratio in terms of down time.
Chemical or solvent systems while effective and widely utilized in the industry are nevertheless costly and present environmental problems in the removal and disposal of the chemical solvents or agents. As a result a number of other mechanical, electrical and magnetic systems have been proposed for the removal or reduction of the amount of paraffin deposits resulting from the transmission of crude oil. The most pertinent prior art system known pertaining to preventing the buildup of paraffin by attempting to control electrostatic forces by the insulation of the pump and tubing from the well casing and the ground attributes paraffin accumulates in oil wells as a result of the actions of electric currents resulting from friction between the moving parts of the well pumping machinery. In U.S. Pat. No. 2,368,777 the friction problem is solved by insulating ground with non conductive washers at such points and in such a manner as to prevent the flow of electric current between the parts and the earth. As such various insulation sleeves and washers are provided between the pumping apparatus and the downhole oil string to reduce the effects of friction and the electrostatic forces which are believed to charge particles in the flow line and cause them to deposit on the inside of the crude oil conduit.
U.S. Pat. No. 2,368,777 does not utilize a special coupling in the oil flow line to dissipate and prevent the building up of the electrostatic forces resulting from the flow of crude oil in flow lines or prevent the deposition of paraffin inside above ground flow lines. U.S. Pat. No. 2,368,777 furthermore does not utilize magnets or the combination of materials of different conductivity and magnetivity in accordance with the present invention for the purpose of not only dissipating frictional forces along the section of the pipe but also to magnetically charge the particles of the constituents of crude oil flowing inside the pipe so as to prevent the subsequent deposition of paraffin, salts and paraffin scale deposits further along the downhole oil string or thereafter in the above ground pipeline or flow line.
U.S. Pat. No. 3,222,878 represents the closest prior art uncovered which pertains to the use of magnetic forces for the purposes of controlling the build up of paraffin deposits in above ground flow lines. U.S. Pat. No. 3,222,878 is not applicable to downhole oil lines in view of the size and arrangement of magnets. This patent appears relevant at first glance but is not particularly relevant to the present invention since U.S. Pat. No. 3,222,878 does not electrically isolate sections of pipe either along the downhole oil string or in surface or subsurface oil transmission flow lines and does not disclose a practical system in terms of practicability or in terms of economic feasibility.
U.S. Pat. No. 3,222,878 does not pertain to a downhole device for oil string lines but pertains only to a device for above ground oil flow lines to prevent the deposition of paraffin and diamagnetic deposits including scale since the arrangement of magnets having a radius of 4 5/16th of an inch could not be utilized downhole since it would not fit down inside an oil string casing which typically are 2 or 21/2 inches (5.1 to 6.4 cm) in diameter. The above ground magnetic system of U.S. Pat. No. 3,222,878 furthermore does not electrostatically isolate sections of pipe and requires magnets disposed along the length of the pipe from about 10 to perhaps 150 times the length of the magnetic field. The length of the magnetic field described in U.S. Pat. No. 3,222,878 is produced from a magnet of about 5 15/16th of an inch (15.08 cm) in length which therefore would require repeating the installation of the arrangement of magnets every 5 to about 75 feet ( 1.5 to 22.9 meters) along the length of the pipe. Therefore even if such a mechanical system could be employed downhole it would be far in excess of the $150 to $600 a month per well and as a result of these and other problems such systems as U.S. Pat. No. 3,222,878 have generally resulted in the industry not accepting magnets and magnetic systems for the control of paraffin.
As a result there is a need for an effective, efficient and inexpensive system for preventing the deposition of paraffin and build up of paraffin, salt and shale combinations on the inside of oil string production lines and above and below ground flow lines that does not interfere with the oil production capabilities of existing wells. The reduction of crude oil production in high paraffin content wells is further compounded by the build up of paraffin in flow lines which require extensive and costly maintenance and have also raised environmental concerns over the elimination of solvents and other materials after dissolving paraffin from the oil lines.
The method of the invention and oil tools constructed in accordance therewith employ a combination of magnetic forces together with the isolation of sections of the crude oil conduits to break up the electrical conductivity and the propagation and build up of electrostatic charged in crude oil conduits by introducing a non magnetic and non electrically conductive liner surrounded by magnets along with a magnetic augmenting shield to magnetically charge crude oil constituents in oil conduits to provide an economically effective oil tools and method to prevent and remove paraffin and paraffin salt, shale combination on the inside of oil transmission pipes. The combination of the non magnetic substantially non electrically conductive liner of the novel oil tools and couplings together with magnets are believed to both disrupt the propagation of electrostatic forces that are believed to assist in the deposition of paraffin and paraffin combination deposits on the pipe wall while at the same time magnetically charging the particles to prevent their deposition on the downhole oil string or above ground flow line for distances of 1,200 feet (366 meters) or more utilizing magnets of about 13/4 inch in length ( 3.5 cm).
The novel oil tools constructed in accordance with the invention that employ a combination of magnetic and non magnetic materials together breaking up the propagation of electrostatic charges unlike the prior art provides for the disposition of magnets along the path of flow of about 6,000 times the dimension of the magnetic field. The method of the present invention therefore allows the disposition of magnets at 1,200 or more feet intervals as opposed to 75 feet intervals of the prior art and allows the device of the present invention to be utilized both in above ground in oil flow lines and below ground in downhole oil strings at an economically and environmentally attractive alternative to the utilization of chemicals, solvent or systems for heating oil, water, solvents or combinations thereof to remove and prevent clogging of crude oil conduits.